Fuel injection valve

ABSTRACT

A fuel injector, especially an injector for fuel injection systems in internal combustion engines, has a piezoelectric or magnetostrictive actuator. The actuator, via a valve needle, activates a valve-closure member, which cooperates with a valve seat surface to form a sealing seat. The actuator can be actuated in a first direction of motion. In contrast, the valve-closure member can be moved by the valve needle in a second direction of motion ( 40 ) that is essentially perpendicular to the first direction of motion.

FIELD OF THE INVENTION

The present invention relates to a fuel injector.

BACKGROUND INFORMATION

U.S. Pat. No. 4,803,393 describes a fuel injector known for fuelinjection systems in internal combustion engines, which is executedusing a piezoelectric actuator. Using the actuator, a valve-closuremember, which cooperates with a valve seat surface forming a sealingseat, can be actuated via a valve needle. The actuator can be actuatedin a first direction of motion, and the valve-closure member can bemoved by the valve needle in a second direction of motion that isessentially perpendicular to the first direction of motion. Between theactuator and the valve needle, a hydraulic transmission device isprovided, the actuator being connected, via a first transmission piston,to a transmission chamber of the transmission device, the chamber beingfilled with a hydraulic fluid and being essentially bent in an L-shape,and the valve needle being connected thereto via a second transmissionpiston. The known fuel injector can only be used as a so-calledinward-opening fuel injector.

German Published Patent Application No. 195 00 706, describes a fuelinjector. In the fuel injector described in this publication, apiezoelectric actuator is provided for actuating a valve needleconnected to a valve-closure member. The valve-closure member cooperateswith a valve seat surface to form a sealing seat. In this context, bothan embodiment as a fuel injector opening to the outside as well as anembodiment as a fuel injector opening to the inside are possible.Although the piezoelectric actuator, assembled from a plurality ofpiezoelectric layers arranged in a stack, generates relatively stronglifting forces, it nevertheless generates relatively short valvetravels. In the above-mentioned printed publication, it is thereforeproposed to provide a hydraulic transmission device to increase thevalve travel, between the valve needle and the piezoelectric actuator,transmitted to the valve needle.

One disadvantage in this known design is that, on the basis of theactuating elements, arranged serially one after the other, and made upof the piezoelectric actuator, the hydraulic transmission device havingthe transmission pistons, and the valve needle, the resulting design isrelatively elongated. The known fuel injector therefore extendsrelatively far out of the cylinder head of an internal combustionengine, which is unfavorable for the assembly process, especially if theinternal combustion engine is one that has four valves and only onecamshaft.

In addition, it is disadvantageous that, for the transmission device, aspecial hydraulic fluid is used, which can escape due to leakage lossoccurring over time. This can impair the mode of functioning of thetransmission device and the service life of the fuel injector.

German Patent No. 43 06 073 describes a fuel injector having apiezoelectric actuator of a different design. In this fuel injector, atransformation of the motion of the piezoelectric actuator to the motionof the valve needle also occurs by way of a hydraulic transmissiondevice. In the fuel injector known from this printed publication, thepiezoelectric actuator, a lifting piston cooperating with thetransmission device, and the valve needle are arranged serially oneafter the other, so that the resulting type of construction isrelatively long. In addition, the potential leakage loss of thehydraulic fluid is disadvantageous here as well.

SUMMARY OF THE INVENTION

In contrast, the fuel injector according to the present invention hasthe advantage that, due to the bent, lateral arrangement of theactuator, the result is a smaller longitudinal extension in the fuelinjector according to the present invention. In this context, theactuating direction of the actuator runs essentially perpendicular tothe movement direction of the valve-closure member and of the valveneedle. As a result of the lateral arrangement of the actuator, the fuelinjector protrudes from the cylinder head less than in the case of thefuel injectors known from the related art, so that the installationspace for the camshaft, intake and outlet valves, a spark plug, andother components of the internal combustion engine is not reduced.Especially in an internal combustion engine having four or more valvesper combustion chamber and only one camshaft, there is, for the fuelinjectors, only a limited installation space available, which is used inthe design according to the present invention in a space-saving manner.

The change in the direction of motion of the actuator, which is actuatedperpendicular to the direction of motion of the valve-closure member, isadvantageously effected by a hydraulic transmission device. Thehydraulic transmission device, in this context, fulfills a doublefunction: first, it is used for transforming the lift, in order totransform the relatively small actuating lift of the actuator into arelatively large lift of the valve-closure member; second, it is used tochange the direction of motion from the direction of motion of theactuator to the direction of motion of the valve needle and of thevalve-closure member, which are perpendicular to the former.

It is advantageous in this context that the hydraulic transmissiondevice is configured such that a transmission chamber filled with ahydraulic fluid is bent in an L-shape. In this context, a firsttransmission piston actuated by the actuator is connected to a first armof the transmission chamber, and a second transmission piston acting onthe valve needle is connected to a second arm of the transmissionchamber. If the fuel injector is one that opens to the inside, thesecond arm of the transmission chamber is advantageously situated on theside of the second transmission piston facing the valve-closure member,in order to generate a lifting motion directed to the inside.Conversely, the second arm of the transmission chamber is situatedadvantageously on the side of the transmission piston facing thevalve-closure member, if the fuel injector is one that opens to theoutside.

The fuel supplied to the fuel injector and spray-discharged by the fuelinjector is used as the hydraulic fluid for the transmission device.Therefore, no special hydraulic fluid, for example, a hydraulic oil,needs to be put into the fuel injector, which could escape due toleakage loss over time. Rather, a quasi-static fuel is continuallyreplenished as the hydraulic fluid, automatically via guide apertures.

A biasing element advantageously surrounds the actuator in a sleeve-likemanner. In comparison to a serial arrangement of the biasing element andthe actuator, this increases the compactness of the fuel injectoraccording to the present invention.

The valve needle is preferably composed of two valve needle segments, afirst valve needle segment being designed as a single piece so as toinclude one of the transmission pistons, and the other valve needlesegment is configured as a single piece so as to include thevalve-closure member. The two valve needle segments can be connected bya coupling piece in a simple fashion. This makes assembly of the fuelinjector according to the present invention significantly simpler.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an axial cutaway view of a first exemplary embodiment ofa fuel injector according to the present invention.

FIG. 2 depicts an axial cutaway view of a second exemplary embodiment ofthe fuel injector according to the present invention.

DETAILED DESCRIPTION

FIG. 1, in an axial section representation, depicts a first exemplaryembodiment of fuel injector 1 according to the present invention. Fuelinjector 1 is especially suited for directly injecting fuel, inparticular gasoline, into the combustion chamber preferably of amixture-compressing, spark-ignited internal combustion engine.

Fuel injector 1 according to the present invention has a first housingbody 2, in which a piezoelectric actuator 3 is integrated. Piezoelectricactuator 3 is composed of a plurality of plates, arranged in a stack andmade of a piezoelectric material. The plates are each provided withelectrodes, which can be connected to two poles of an electrical powersource, such that the electrical field direction in each of the platesruns in the same axial direction. Of course, instead of a piezoelectricactuator, a magnetostrictive actuator can also be used in the same way.Piezoelectric actuator 3 is supported, so as to be mechanically biased,by a biasing element 4, which surrounds piezoelectric actuator 3 in asleeve-like manner, through two tension springs. Piezoelectric actuator3 is gripped between a first actuator flange 5 and a second actuatorflange 6, sleeve-like biasing element 4 being connected, via fasteningelements 7 and 8, to first actuator flange 5 or to second actuatorflange 6 in a force-locking manner. Piezoelectric actuator 3, biasingelement 4, and both actuator flanges 5 and 6 are inserted into a firstcylindrical recess 9 of first housing body 2. In a second cylindricalrecess 10, which is connected to first cylindrical recess 9, a firsttransmission piston 11, to be describing greater detail below, isinserted. The axial position of actuator 3, actuator flanges 5 and 6,and first transmission piston 11, which is axially impacted upon bysecond actuator flange 6, can be adjusted using an adjusting element 12,which is connected via a thread 13 to first housing body 2 and which atthe same time constitutes the external termination of recess 9. Theaxial adjustment of adjustment element 12 is performed by being twistedusing a tool that can be inserted into a tool depression 14.

First housing body 2 is bolted to a second housing body 16 via a thread15, second housing body 16 having a lateral receptacle 17, so that firsthousing body 2 can be screwed in. In second housing body 16, a fuelsupply line 18 is integrated, which leads from a fuel intake feed pipe19 to a recess 20. Disposed at the end opposite fuel intake feed pipe 19is a valve seat body 21, which is biased against second housing body 16by a tightening nut 22, so that a recess 23 of valve seat body 21 isconnected to recess 20 of second housing body 16.

On valve seat body 21, a truncated-cone-shaped valve seat surface 24 isformed, which cooperates with a conical segment 25 of a valve-closuremember 26 forming a sealing seat. A cylindrical section 27 ofvalve-closure member 26 is provided with at least one swirl groove 28,which assures an optimal distribution of the fuel. Connected tovalve-closure member 26 is a spray-discharged opening 29 in valve seatbody 21.

Valve-closure member 26 is actuated by a valve needle 30, which in thedepicted exemplary embodiment is composed of a first valve needlesegment 30 a, configured as a single piece so as to include a secondtransmission piston 35, and a second valve needle segment 30 b, which isconfigured as a single piece so as to include valve-closure member 26.First valve needle segment 30 a and second valve needle segment 30 b areconnected to each other by a coupling piece 31. In this context, firstvalve needle segment 30 a and second valve needle segment 30 b have agroove 33 a and 33 b, respectively, into which coupling piece 31 issnapped, thus forming a form-locking connection between first valveneedle segment 30 a and second valve needle segment 30 b. In thiscontext, first valve real segment 30 a can be preassembled on secondhousing body 16, and fuel injector 1 can be assembled by first addingsecond valve needle segment 30 b having valve-closure member 26 to firstvalve needle segment 30 a and connecting it to coupling piece 31.Finally, valve seat body 21 can be mounted and can be biased with regardto second housing body 16 using tightening nut 22 via thread 34.

For the resetting of valve needle 30 and valve-closure member 26, thereis a resetting spring 36, which is fixed between second transmissionpiston 35 and a cover element 37 of second housing body 16.

First transmission piston 11 and second transmission piston 35 are partsof a transmission device 38. Transmission device 38, in addition to twotransmission pistons 11 and 35, includes a transmission chamber 41,which is filled with a hydraulic fluid. In this context, firsttransmission piston 11, which is in an operative connection withactuator 3, borders on transmission chamber 41 at a first surface A1,which is dimensioned so as to be larger than a second surface A2, atwhich second transmission piston 35, which is in connection with valveneedle 30, borders on transmission chamber 41.

The functioning of fuel injector 1 according to the present invention isas follows:

By acting upon piezoelectric actuator 3 through an electrical actuationvoltage, the actuator expands axially and, via second actuator flange 6,moves first transmission piston 11 in FIG. 1 to the right, in a firstdirection of motion 39. Transmission device 38 transforms this firstdirection of motion 39 into a second direction of motion 40,perpendicular to the first, of valve needle 30 and valve-closure member26. In this context, first transmission piston 11 presses the hydraulicfluid located in transmission chamber 41, such that second transmissionpiston 35, and therefore valve needle 30 and valve-closure member 26 inFIG. 1, are moved upwards. Since surface A1 of first transmission piston11 is dimensioned so as to be larger than surface A2 of secondtransmission piston 35, the valve lift transmitted to valve needle 30 islarger than the actuating lift exerted by actuator 3.

Transmission device 38, in this context, has two functions: first,redirecting first direction of motion 39 into a direction of motion 40,perpendicular to the first, and, second, transforming the relativelysmall actuating lift of actuator 3 into the increased valve lift ofvalve needle 30 and valve-closure member 26.

In the exemplary embodiment depicted, transmission chamber 41 isconfigured so as to be bent in an L-shape. In this context, transmissionchamber 41 has a first arm 42, which is connected to first transmissionpiston 11, and a second arm 43, which is connected to secondtransmission piston 35. This design of transmission chamber 41 has theadvantage that the volume of transmission chamber 41 is small.

Since fuel injector 1, according to the exemplary embodiment depicted inFIG. 1, is one that opens to the inside, second arm 43 of transmissionchamber 41 is advantageously situated on the side of second transmissionpiston 35 that faces valve-closure member 26, in order to achieve avalve lift to the inside, i.e., in FIG. 1, upwards.

The hydraulic fluid located in transmission chamber 41 is preferably thefuel fed from fuel intake feed pipe 19 via fuel supply line 18, recesses20 and 23, and swirl groove 28, to the sealing seat formed byvalve-closure member 26 and valve seat surface 24. The fuel can bereplenished in a quasi-static manner in transmission chamber 41 via aguide aperture between second housing body 16 and first valve needlesegment 30 a. Of course, this guide aperture should be dimensioned so asto be small enough that when fuel injector 1 is actuated, the fuel,operating as the hydraulic fluid, cannot escape from transmissionchamber 41 through this guide aperture, or does so in practicallynegligible amounts. Using the fuel as a hydraulic fluid has theadvantage that a special hydraulic fluid, for example, a specialhydraulic oil, is not necessary. In this context, no danger arises thata special hydraulic oil could contaminate the fuel. The possibility oflosses due to leakage of the hydraulic fluid is compensated for bycontinual replenishment. The standing pressure of the fuel system shouldbe greater than the vapor pressure of the fuel.

In FIG. 2, a second exemplary embodiment of a fuel injector 1 accordingto the present invention is depicted. In contrast to fuel injector 1,opening to the inside and depicted in FIG. 1, fuel injector 1 depictedin FIG. 2 is a fuel injector I that opens to the outside. Elementsdescribed on the basis of FIG. 1 are furnished with the same referencenumerals, so that to this extent no repeat description is necessary.

Valve-closure member 26 is situated on the exterior side on valve seatbody 21. Valve seat body 21 on its external side has a valve seatsurface 24, which cooperates with a conical segment 25 of valve-closuremember 26 forming a sealing seat. Upstream of conical segment 25,valve-closure member 26 has a constriction 50, which is connected via aflattened area 51 of valve needle 30 to a recess 23 of valve seat body21. The fuel flows through a fuel intake feed pipe 19 and through fuelsupply line 18 to recess 23 of valve seat body 21 and continues, via theaperture remaining between flattened area 51 and surrounding valve seatbody 21, to the sealing seat formed by conical segment 25 ofvalve-closure member 26 and valve seat surface 24. In this context,valve-closure member 26 is biased against valve seat surface 24 byresetting spring 36. Resetting spring 36 engages at a flange 52, whichpresses against a locking ring 54, inserted into a groove 53 of valveneedle 30, and which therefore is connected in a form-locking manner tovalve needle 30.

Transmission chamber 41 of transmission device 38 is also configured inthe exemplary embodiment depicted in FIG. 2 as bent in an L-shape, firsttransmission piston 11, in an operative connection with actuator 3 viathe actuator flange 6, and second transmission piston 35, in anoperative connection with valve needle 30, being connected to a secondarm 43 of transmission chamber 41.

When actuator 3 is activated, it extends in the direction of housingbody 16 and pushes first transmission piston 11 to the left, inaccordance with first direction of motion 39 in FIG. 2. Since second arm43 of transmission chamber 41 in the exemplary embodiment depicted inFIG. 2 is located on the side of second transmission piston 35 that isfacing away from valve-closure member 26, second transmission piston 35is pushed downwards, in accordance with second direction of motion 40 inFIG. 2. Second transmission piston 35, in this context, presses againstvalve needle 30 and pushes it downwards, together with valve-closuremember 26 in FIG. 2, in order thus to open fuel injector 1. After theelectrical power activating actuator 3 is switched off, valve needle 30and valve-closure member 26, connected thereto, are reset by resettingspring 36, until valve-closure member 26 is again sealingly contactingvalve seat surface 24.

A further difference in the exemplary embodiment depicted in FIG. 1 withrespect to the exemplary embodiment depicted in FIG. 2 lies in the factthat first transmission piston 11 is integrated not in first housingbody 2 but rather in second housing body 16.

To compensate for any leakage losses, in the exemplary embodimentdepicted in FIG. 2, transmission chamber 41 is replenished through anarrow guide aperture between second transmission piston 35 and secondhousing body 16.

The present invention is not limited to the exemplary embodimentsdepicted. For example, instead of a piezoelectric actuator 3, amagnetostrictive actuator can be used in the same manner.

What is claimed is:
 1. A fuel injector, comprising: one of apiezoelectric actuator and a magnetostrictive actuator, a valve needle;a valve-closure member that is actuated by the one of the piezoelectricactuator and the magnetostrictive actuator via the valve needle; a valveseat surface with which the one of the piezoelectric actuator and themagnetostrictive actuator cooperates to form a sealing seat, wherein:the one of the piezoelectric actuator and the magnetostrictive actuatoris capable of being actuated in a first direction of motion, and thevalve-closure member is capable of being moved by the valve needle in asecond direction of motion that is essentially perpendicular to thefirst direction of motion; a hydraulic transmission device arrangedbetween the one of the piezoelectric actuator and the magnetostrictiveactuator and the valve needle; a first transmission piston via which theone of the piezoelectric actuator and the magnetostrictive actuator isconnected to a transmission chamber of the hydraulic transmissiondevice; and a second transmission piston via which the valve needle isconnected to the transmission chamber; wherein: the transmission chamberis filled with a hydraulic medium and is essentially bent in an L-shape,a first surface of the first transmission piston, at which the firsttransmission piston is connected to a first arm of the transmissionchamber, is larger than a second surface of the second transmissionpiston, at which the second transmission piston is connected to a secondarm of the transmission chamber, the fuel injector opens to the outside,and the second arm is arranged on a side of the second transmissionpiston that is facing away from the valve-closure member.
 2. The fuelinjector according to claim 1, wherein: the fuel injector corresponds toan injector for a fuel injection system in an internal combustionengine.
 3. The fuel injector according to claim 1, further comprising: aflange connected to one of the valve needle and to the secondtransmission piston; and a resetting spring engaged with the flange. 4.The fuel injector according to claim 1, wherein: a fuel that is suppliedin the fuel injector to the sealing seat corresponds to a hydraulicfluid with which the transmission chamber is filled.
 5. The fuelinjector according to claim 1, further comprising: a biasing elementsurrounding the one of the piezoelectric actuator and themagnetostrictive actuator in a sleeve-like manner.
 6. The fuel injectoraccording to claim 1, further comprising: a coupling piece, wherein: thevalve needle includes: a first valve needle segment configured as asingle piece so as to include the second transmission piston, and asecond valve needle segment configured as another single piece so as toinclude the valve-closure member, and the first valve needle segment isconnected via the coupling piece to the second valve needle segment.